I. Field of the Invention
Embodiments of the present invention relate generally to medical devices for treating certain vascular abnormalities, such as aneurysms. In particular, embodiments are directed to medical devices and methods for occluding vascular abnormalities in areas of a patient's neuro-vasculature such as the carotid artery.
II. Description of the Related Art
Various types of intravascular medical devices, both biological and synthetic, have been used for a large array of reparative vascular procedures, such as to treat obstructive vessels and aneurysms. An aneurysm, for example, is an abnormal widening or ballooning of a portion of an artery due to damage to or weakness in the wall of the blood vessel. Weaknesses in the blood vessel wall may be caused by medical conditions, such as arteriosclerosis, or may be congenital. As blood flows past the weakened area, the affected vessel wall thins over time and expands like a balloon, which can eventually burst if the vessel wall gets too thin.
The goal of therapy for aneurysms is to prevent the blood vessel from rupturing. Once an aneurysm has ruptured, for example in arteries leading to the brain, a stroke may occur and brain damage or even death may result if the patient does not receive immediate treatment. Brain damage or death may be avoided, however, if the aneurysm is detected and treated at an early stage, ideally when the aneurysm is relatively small, using a lower risk procedure.
Aneurysms may be treated with surgery. The surgical procedure for treating some types of aneurysms involves replacing the affected portion of the blood vessel with a synthetic graft, which may comprise a tube made out of an elastomer or polymer material with properties that are intended to substitute the function of a normal, healthy vessel. Due to limitations in reaching certain brain aneurysms, however, surgical treatment may not be an option. Moreover, even in accessible areas, surgical treatment is still complex and may pose additional risks to the patient, especially for the elderly.
More recently, instead of performing surgery to repair an aneurysm, an intravascular medical device, such as an endovascular stent or stent-graft, may be delivered to the site of the aneurysm using an elongated catheter. In other cases, the aneurysm may be filled with metallic coils or other embolic materials that are delivered through small catheters to cause clot formation and tissue growth within the aneurysm and to strengthen the wall and reduce the effect of blood pressure on the wall of the aneurysm, thereby reducing the likelihood of rupture. An endovascular stent-graft, for example, is a tube that includes a blood-impervious fabric supported by a metal stent. It can be used to treat a variety of conditions involving blood vessels, but most commonly is used to reinforce a vessel wall at the site of an aneurysm.
Depending on the size, shape, and location of the aneurysm various types of medical devices may be required to reinforce the vessel wall. For example, aneurysms occurring in the carotid artery may not allow for a sufficient “landing zone” proximal to and distal from the ends of the stent-graft for proper placement and maintaining of the medical device in position.
Aneurysms can be defined as wide-necked or narrow-necked aneurysms. Current therapies for treating wide-necked aneurysms include placing a stent over the lesion and introducing coils into the aneurysm. The stent acts as a gate and prevents the coils from falling out as there is minimal neck present. Some aneurysms, known as “berry” aneurysms, are very small and spherical in shape. Berry aneurysms typically have a narrow neck and often occur near or at a branch of an artery. Conventional methods of filling these aneurysms have limitations. For example, small metallic coils may not adequately fill the aneurysm and may embolize or protrude into the native vessel. Over-filling the aneurysm may further weaken the aneurysm. Liquid embolics that solidify in blood may also embolize or inadequately fill or seal the aneurysm, and the solidification process may release chemicals into the blood stream.
Accordingly, there is a need for an improved medical device designed to address vascular aneurysms, and particularly neuro-vascular aneurysms such as berry aneurysms in locations such as the carotid artery, the basilar artery, the Circle of Willis, the maxillary artery, the facial artery, and the vertebral artery that is capable of being deployed using smaller-diameter delivery devices, that is flexible enough for delivery through tortuous sections of vasculature, that provides effective and rapid exclusion at the target site, that is able to maintain its vascular position, that does not interfere with the normal flow of blood, and that overcomes the shortcomings of conventional solutions.